Magnetic unloader



June Z, 1936. c. E. PL oEGER MAGNETIC UNLOADER Filed Aug. 8, 1933 lll/lll Patented June 2, 1936 UNITED STATES 2,043,059 l mamme UNLoanEa Clyde Alt. Ploeger, Evansville,

Ind., assigner to Servel, Inc., New York, N. Y., a corporation of Delaware Application August 8, 1933, lSerial No. 684,147

11 Claims.

This invention relates to unloaders ier electric motors, especially motors for operating refrigeration systems of the compression type, and generally oi the type disclosed in my copending application Serial No. 483,148 of which the present application is a continuation in part.

In my said earlier application there is disclosed an unloader for an electric motor having anpactuating member of magnetic material which 0 is adapted to be so positioned with respect to the motor that it is attracted by the strong leakage magnetic field during the starting period oi the motor and is retracted by suitable means such as a spring or gravity when the leakage field decreases upon attainment of normal speed. 'I'here is illustrated in my said application a vertical compressor-unit of anhermetically sealed refrigeration system, the compressor being provided with an unloading valve actuated by a magnetic EO ring located above the upper end of the motor where it is attracted upon increase of leakage ux and retracted by a spring upon decrease in the leakage flux. As set forth in my said earlier application, the magnetic actuating member may be retracted by gravity means instead of a spring.

In accordance withthe present invention I provide a gravity biased unloader for the motorcompressor unit of a refrigeration apparatus which is compact in construction and eicient in 0 operation.

from the following description taken in connection with the accompanying drawing, in which,

Fig. 1 shows diagrammatically a refrigeration system including a motor-compressor unit in vertical section illustrating one application of the invention;

Fig. 2 is a fragmentary section of the unit taken on line 2--2 in Fig. 1; and 40 Fig. 3, a bottom plan view of only the unloader linkage shown in Figs. 1 and 2.

Referring to the drawing, an hermetically sealed casing I0 encloses the motor-compressor unit of a refrigeration system. Within the cas- 45 ing Ill is secured a frame Il 'provided with a vertical thrust bearing I2. As shown, the frame II may be secured by a shrink-lit within the upper reduced portion of the casing I0. Within the upper part of the casing there is an electric in- 50 duction motor comprising a stator I3 and a rotor Ill. The stator ismounted on the frame I I within the reduced portion of the casing I0, as shown, for good heat dissipation. To increase heat radiation from the unit, the upper reduced portion 55 of the casing Il! may be provided with radiation (Cl. (i2-4) fins, not shown. The rotor I4 is mounted on the upper end of a vertical shaft I5 which is journaled in the bearing I2.

The lower end of the shaft I5 is provided with a crank I6 journaled in a cylindrical crosshead 5 I1. 'I'he latter is reciprocable in a tubular yoke I8 to which is secured the compressor piston I9. The latter is reciprocable in a cylinder mounted on the underside of the frame II. The compressor cylinder 20 is provided with an intake 10 port 2I controlled by a flexible flap valve 22 and a discharge port 23 controlled by a valve 24.

The discharge side of the compressor is connected through a conduit 25 to the condenser and the latter is connected through an expansion l5 valve to the evaporator. From the latter a suction line 26 is connected to the motor-compressor unit casing I0. In operation, a suitable refrigerant gas, for instance methyl chloride, is .discharged under pressure from the compressor to 20 the condenser where the refrigerant is condensed to liquid. The liquid is admitted to the evaporator from the condenser through the expansion valve which maintains a pressure difference between these two elements. In the evaporator the 25 liquid vaporizes to produce a refrigerating eil'ect, as well known in the art, and the refrigerant vapor returns through conduit 26, the chamber enclosed by the casing III, and intake port 2| to the compressor, thus completing the refrigerant 30 cycle.

The compressor cylinder 20 is provided with a pressure relief or unloading valve indicated generally by the reference numeral 21. The valve member, comprising a needle 28, is urged by a.

small spring 29 to the open position in which pressure within the compressor cylinder 2D is relieved into the chamber enclosed by the unit casing Ill, thus controlling a connectionl from the high pressure to the low pressure side of the compressor.

Below the electric driving motor an annular member 30 of magnetic material is positioned in such a manner as to be linked by the magnetic 'leakage iiux of the motor. As shown, the mag- 45 netic member 30 may be guided for vertical reciprocation by that portion of the frame II in which is mounted the bearing I2. Depending from the magnetic ring 30 are diagonally opposite studs 3l which are preferably made adjust- 50 able by threading into corresponding tapped bosses 32 on the magnetic member 30. These studs 3i extend through guide openings 33 in the frame Ii and rest in operative engagement upon the ends t4 of a bifurcated lever 35. The other 55 end of thev lever 35 is suitably pivoted on the underside of the frame II so that the lever rests in operative engagement upon the unloading valve 21.

5 The weight of the member 30 resting on the ends 34 of the lever 35 is suiiicient to normally force the unloading valve needle 28 downwardly to its closed position, thus cutting oilr communication between the high and low4 pressure sides of the compressor. However, when the circuit of the motor is closed while the rotor is at a standstill, excessive currents ilow in both leld and armature windings causinga distortion of the magnetic iiux which extends beyond the normal magnetic path and creates a strong magnetic leakageiield. 'I'he magnetic annulus 30, being positioned within said leakage iield, is attracted upwardly, thus removing its weight from the ends of the lever 35, whereupon the unload- 2o ing valve 21 is opened by the spring 29 to equalize the pressures on the high and low sides of the compressor. Upward movement of the magnetic member 3U is limited to prevent contact, with the motor by iianged sleeves 36 threaded on the studs 3|. The sleeves 36 may be adjusted to vary the distance through which member moves. As the rotor comes up to speed, the current in the windings decreases and the strength of the leakage eld diminishes, whereupon the 30 magnetic member 30 drops back under the force of gravity to reclose the unloading valve 21. It will be understood that the magnetic member 30 is heavy enough to prevent movement due to the magnetic eld of the motor during normal operation and also to close the valve 21 against the action of the spring 29. It is clear that the lever 35 may be directly connected to operate the valve 21 and the magnetic member 30 directly connected to the lever 35 thereby carrying out the above operation of the valve 21 without the provision of the spring 29.

Lubricating oil is supplied from the sump formed by the bottom of the casing I 0 to the bearing I2 by suitable means such as a pump,

not shown. Such lubrication means forms no part of this invention but Vis preferably of the type disclosed in Patent No. 1,910,498 to Ploeger et al. of May 23, 1933, in which oil is pumped through the hollow motor shaft to the bearing.

Some of the lubricating oil, which is fed to the bearing I2 under pressure, escapes from the upper end of the bearing and ows downwardly within the ilange 31 of the rotor I4 into the trough 36 of the tray-like operating member 30 into which the flange 31 extends. The oil drains from the trough 30 and through the frame I I back to the lower part of casing I0 by way of one or more drain holes 38. 'I'he latter may be arranged for distribution of oil over parts therebelow in the lower part of the casing.

It will be obvious to those skilled in the art that various other changes may be made in the construction and arrangement without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawing and described in the specification but only as indicated in the following claims.

I claim:

1. In combination with a compressor driven by an electric motor, an unloading valve for said compressor, and means for actuating said valve including an annular member of magnetic material vertically reciprocable below said motor so 75 as to be raised against the force of gravity upon speed, means connected to increase in strength of the magnetic leakage field of said motor.

2. In combination, a compressor, a vertical electric motor above said compressor, a driving connection between said motor and compressor, 5 an unloading valve for said compressor, and actuating means for said valve including an annular member of magnetic material encircling said driving connection and vertically reciprocable adjacent said motor so as to be raised against 10 the force o1' gravity upon increase in strength of the magnetic leakage field of said motor, and a lever operatively connecting said valve and said annular member.

3. In a refrigeration system of the compression l5 type, a motor-compressor unit comprising a vertical electric motor having a shaft operatively connected at its lower end to a compressor, an unloading valve for said compressor, and actuating means for said valve comprising an annular 20 member of magnetic material encircling said shaft below the motor and guided for vertical reciprocation within the magnetic leakage field of the motor and a lever operatively engaging said valve and having a bifurcated end strad- 25 dling said motor shaft in operative engagement with said annulus at diagonally opposite points thereof.

4. In a refrigerating system, a motor compressor unit, a reciprocable member located below 30 said motor, an unloading valve for the compressor, an element associated with said valve and disposed in the path of movement of said reciprocable member, the construction being such that movement of the reciprocable member in one 35 direction will permit the valve to open and movement in the opposite direction will cause the valve to close.

5. An electric motor, a reciprocable member of magnetic material mounted axially of said motor 40 and attractable upon increase in strength of the magnetic leakage field of the motor at the time of starting and being constructed to return to its original position after the motor has attained speed, means connected to be driven by said 45 motor whereby a load is imposed on said motor, means for relieving the motor of its load, and means associated with said last mentioned means and disposed in the path of movement of said reciprocable member in a manner to be operated 50 thereby.

6. An electric motor, a reciprocable member of magnetic material mounted axially of said motor and attractable upon increase in strength of the magnetic leakage field of the motor at the time 55 of starting and being constructed to return to its original position after the motor has attained be driven by said motor whereby a load is imposed on said motor, means for relieving the motor of its load, means 50 associated with said last mentioned means and disposed in the path of movement of said reciprocable member in a manner to be operated thereby, and adjustable means between said reciprocable member and member extending in its path 65 for varying the amount of movement of said load relieving member.

- 1. A motor compressor unit for a refrigerating system comprising a casing, a partition member in said casing dividing said casing into upper 70 and lower chambers, said partition being provided with a drain orice, whereby liquid can pass by gravity from the upper chamber to the lower,

a bearing mounted centrally of said partition,

a shaft journalled in said bearing and having a crank on its lower end, a motor mounted in the upper chamber and having its rotor ixed on said shaft to drive the same upon energization of the motor, a, compressor in said. lower chamber arranged to be driven by said crank, a magnetic member attractable responsive to increase in strength of the magnetic leakage fi'eld of the motor when starting, an unioader valve 'associated with the compressor, and a connection between said reciprocable member and said valve whereby said valve will be operated by said magnetic. member.

8. A motor compressor unit for a refrigerating system comprising a casing, a partition member in said casing dividing said casing into upper and lower chambers, said partition being provided with a drain orifice, whereby liquid can pass by gravity from the upper chamber to the lower, a bearing mounted centrally of said partition, a shaft journalled in' said bearing and having a crank on its lower end, a motor mounted in the lupper chamber and having its rotor xed on said shaft to drive the same upon energization of the motor, a. compressor in said lower chamber arranged to be driven by said/crank, a magnetic member attractable responsive to increase in strength of the magnetic leakage iield ofl themotor when starting, an unloader valve associated with the compressor, a connection between said reciprocable member and ls aid valve whereby said valve will be operated by said magnetic member, said connection comprising an element disposed in the path of movement of said reciprocable member, and adjustable means for varying the relation between said valve and magnetic member for varying the operation oi said valve;

9. For use with a refrigerating circuit including' a compressor, means to unload said compressor, and a vertically' mounted electric motor for driving said compressor, an actuating member comprising a part of magnetic material vertically reciprocable with respect to said motor so as to be raised in opposition to the force of gravity upon increase in strength of the. magnetic leakage ileld of said motor, and means whereby said actuating means controls said unloading A means.

10. For use with a refrigerating circuit including a compressor, means to unload said compressor, and a vertically mounted electric motor .for driving said compressor, an annular member raised in opposition to the forceoi gravity upon increase in strength of lthemagnetic leakage i'leld of said motor, and means whereby said actuating means controls said unloading means.

CLYDE E. PLOEGER.. 

